A sheet processing apparatus for processing sheets of marketable securities or others has a sheet take-out apparatus and the sheet take-out apparatus takes out and conveys the sheets of a sheet bundle inserted in a batch according to the processing unit one by one. The sheets conveyed one by one are checked for the quality thereof (shape, damage, blurred print, soiled print) by a sheet check device and are sorted and stacked into normal bills (hereinafter, referred to as qualified bills), abnormal bills (hereinafter, referred to as disqualified bills), and rejection bills such as abnormal conveying bills and double feed bills or they are stacked and sealed. For example, qualified bills are bundled (hereinafter, referred to as sealed) by a paper belt as a binding belt every 100 sheets so as to form a bunch and as required, 10 bunches are stacked and sealed additionally by a paper belt to form a bundle.
The sheet take-out apparatus aforementioned, when a failure occurs in the sheet take-out portion or on the conveying path, stops the take-out operation. Further, even when an operator detecting an error stops the take-out, the apparatus stops the take-out operation.
If the take-out apparatus is stopped in this way, the conveyance of sheets is also stopped, so that so as to return sheets remaining on the conveying path to the backup plate, the backup plate moves down (for example, refer to Patent Document 1). Patent Document 1: Japanese Patent Application Publication No. 9-110207 (FIG. 1 shown on page 12)
However, in the sheet processing apparatus stated in the Patent Document 1, when the backup plate moves down, some sheets are adhered to the sheet guide plate (side wall) of the sheet feed portion and fall down on the lower part of the backup plate, so that a problem arises that they may not be processed. Hereinafter, it will be explained in detail by referring to FIGS. 9A to 9C.
FIG. 9A shows the status that when the backup plate moves down because the take-out apparatus is stopped for the reason aforementioned, a sheet Pa hangs down in a sheet take-in port 120c between a take-out rotor 210b and a fixed absorbing unit 120 which compose a take-out apparatus 1b. 
FIG. 9B shows the status that the sheet Pa hanging down in FIG. 9A falls down by its own weight between a sheet bundle Pb and a sheet guide plate 130. Here, the case that the sheet Pa falls down so as to adhere to the side wall is shown.
FIG. 9C shows the case that the sheet remaining on the conveying path due to the obstacle aforementioned is returned onto the sheet bundle Pb loaded on the backup plate 110 and the take-out apparatus 1b is driven again without noticing the fallen sheet Pa. If the backup plate 110 moves up in correspondence to the driving of the take-out apparatus 1b, the sheet Pa stuck to the side wall may fall down on the lower part of the backup plate 110.